There is a clinical need for accurate measurements of a person's oral and nasal respiration. These measurements are of value, for example, in modelling nasal air conditioning, odorant transport and drug delivery. Currently, techniques available to obtain time-accurate measurements of human respiration are limited, and may require complex hardware setups, necessitating clinical visits and considerable discomfort for patients. Alternative, non-intrusive measurement techniques, such as the use of nasal prongs, may be effective but necessarily cannot provide accurate measurements of flow rates.
A previous study (“Nasal inspiratory flow: at rest and sniffing”, Rennie et al., International Forum of Allergy & Rhinology, Vol. 1, No. 2, March/April 2011, hereinafter referred to as “Rennie et al. (2011), and the content of which is incorporated herein by reference in its entirety) documents the use of a hotwire anemometry-based system to quantify the time-varying flow rate during inspiration at rest and in sniffing. This technique was adopted, as a high-precision measurement of the time-evolution of low volumetric flow rates was required, and no alternative measurement technique was available. However, by its very nature, hotwire anemometry is fundamentally inappropriate for this particular application, as it is temperature dependent; this can limit its accuracy, particularly for exhalation measurements which would be affected by a patient's body temperature.
It is, therefore, an object of embodiments of the present invention to seek to alleviate the above identified problems. It is however to be understood that the present invention is by no means limited to respirometry. Rather, the present invention seeks to provide an improved flow meter in general, or at least to provide a useful alternative to existing flow meters.